1. Field of the Invention
The present invention generally relates to hopper containers for dispensing viscous liquid or granular materials and, more particularly, to safety door systems for hopper containers as may be used in such applications as pavement construction or repair or in agricultural uses.
2. Description of the Prior Art
Containers that hold and dispense viscous liquid or granular materials for use in pavement construction or repair or agricultural applications are well known in the art. Such containers may be called hopper bodies and be used in stationary or mobile equipment. Some hopper bodies typically include one or more rotating implements in the interior of the hopper for stirring, agitating or facilitating the dispensing of the material from the hopper, usually from an opening disposed in the lower portion of the hopper. For example, hopper bodies used in asphalt pavement repair vehicles are described in U.S. Pat. No. 5,988,935, issued Nov. 23, 1999 and assigned to the assignee of the present invention. This patent is hereby incorporated by reference into this specification in its entirety.
The hopper bodies of asphalt pavement repair vehicles may be large enough to contain up to four cubic yards, or more, of material. The material may be heated to prepare it for use and agitated by a paddle shaft mechanism to maintain a uniform consistency and temperature. Further, during dispensing of the material, an auger used as a screw conveyor may be used to facilitate the dispensing process. Both the paddle shaft and the screw conveyor may be rotating mechanisms powered by hydraulic motors, for example. In some situations of use, the material in the hopper body may become too viscous or tend to clog the rotating mechanisms during a mixing or dispensing operation. In these or similar situations, operating personnel may be tempted to climb inside the hopper body to attempt to clear a blockage or to manually assist the paddle shaft or screw conveyor in stirring or conveying the material. This is an extremely dangerous activity because it exposes the operating personnel to the risk of serious injury by the rotating implements within the hopper body.
What is needed is a system or method for ensuring that operating personnel are prevented from entering the hopper body while the rotating equipment is operating. Further, even if a worker enters the hopper body for some reason, a system or method is needed for stopping the operation of the rotating machinery or any other moving device within the hopper body to minimize the risk of injury to the person.